This proposal describes a symposium on different facets of the role of adenosine deaminase (ADA) in disorders of purine metabolism and in immune deficiency. Areas which will receive emphasis include reviews of relationships of defects in purine metabolism to immune deficiency in clinical and experimental systems, relationships between the various enzyme activities involved in purine, oligonucleotide and methyl-group metabolism, effects of inhibitors of ADA in Chemotherapy of neoplastic and viral diseases, and the role of purine metabolism in chemotaxis and phagocytosis. The overall objective of the symposium is to provide the most current information in these areas so that critical evaluation can logically lead to the development of effective clinical protocols to treat immunodeficiencies of various etiologies, to improve allograft acceptance, to treat more effectively certain types of neoplastic diseases with ADA inhibitors, to better understand the metabolic effects of drugs which are ADA inhibitors and to be able to relate defects in phagocytic efficacy to immune deficiency and perturbations in purine metabolism. These goals can be met by reviews and discussions of the topics described by individuals intimately involved with the laboratory and clinical research in question. The meeting is planned for New York City as a New York Academy of Sciences Conference, and will be published as a volume in the Annals of the New York Academy of Sciences.